Backport from mainline

	Backport from mainline
	2012-09-12  Ganesh Gopalasubramanian  <Ganesh.Gopalasubramanian@amd.com>

	* config/i386/i386.md : Comments on fma4 instruction selection
	reflect requirement on register pressure based cost model.

	* config/i386/driver-i386.c (host_detect_local_cpu): fma4
	flag is set-reset as informed by the cpuid flag.

	* config/i386/i386.c (processor_alias_table): fma4
	flag is enabled for bdver2.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/branches/gcc-4_7-branch@191227 138bc75d-0d04-0410-961f-82ee72b054a4